What you want doesn't exist.
The Japanese blurays are the best picture quality and are compatible with North American bluray players but do not have subtitles.
There are decent quality import DVDs from Hong Kong (R3, NTSC) and/or Australia (R4, PAL) that have English subs but, as I listed, they are not region free.
As far as I know, no authorized subtitled version of the Japanese cut of KK vs G exists.
For most of the films, I'd suggest getting the Madman R4 discs from Australia. For the ones (G84) that madman didnt put out, or in the event PAL presents an issue for you (or you just can't stand PAL speed up), I'd go with the Hong Kong R3 discs. Both are generally quite cheap and with a little research online it's VERY easy to find an inexpensive DVD player that can be hacked to play all regions and do NTSC/PAL conversion on the fly. I needed a new one about a year ago and was able to find a good player at Best Buy for $40.
EDIT: oh, and I'm not aware of any subtitle release of the Mothra Trilogy.
